Initial Attach on E-UTRAN with Diameter Interfaces

A UE needs to register with the network to receive services that require registration.

The following figure shows the call flow derived from the 3GPP reference for initial attach on E-UTRAN with Diameter interfaces Gx and Gy.

Call Flow for E-UTRAN Initial Attach
Call Flow Description for E-UTRAN Initial Attach
Step Description
1

MME sends Create Session Request to S-GW.

2

S-GW sends Create Session Request to SMF.
Note
As part of this call flow, Secondary Authentication using RADIUS gets enabled in a DNN profile, and the AAA server is selected based on the RADIUS profile configuration.

3

SMF sends RADIUS Access-Request to AAA server for authentication.

4

AAA Server sends Access-Accept to SMF.
Note

SMF assigns IP Address, commonId allocation, and UPF selection. SMF selects PCRF server based on Diameter endpoint profile configuration.

5

SMF sends Gx Credit Control Request Initial to PCRF server requesting for policy.

6

PCRF Server sends Gx Credit Control Answer Initial to SMF.
Note
SMF selects the Online Charging System (OCS) server based on the Diameter endpoint profile configuration.

7

SMF sends Gy Credit Control Request Initial to the OCS server requesting for quota.

Note
If the diameter send- ccri traffic-start is not configured, CCR-I is sent to OCS without any quota request after the Gx response for the default bearer. A successful response from OCS results in continuation of the Initial Attach procedure.

8

OCS server sends Gy Credit Control Answer Initial to SMF.

9

SMF sends Radius Accounting request start to AAA Server.

10

AAA Server sends Radius Accounting Response to SMF.

11

SMF sends N4 PFCP Session Establishment Request to UPF to create PDRs/FARs/QERs/URRs.

12

UPF sends N4 PFCP Session Establishment response to SMF.

13

SMF sends Create Session Response to S-GW.

14

S-GW sends Create Session Response to MME

15

MME sends Router solicitation to S-GW for IPv6 call.

16

S-GW sends Router Solicitation to UPF for IPv6 call.

17

UPF sends Router Advertisement to S-GW for IPv6 call.

18

S-GW sends Router Advertisement to MME for IPv6 call.